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Unit Goals•Describe the phases of the cell cell

cyclecycle.•Describe the process of MitosisMitosis.

–Describe the functions of mitosis.

•Describe the process of MeiosisMeiosis.–Describe the functions of meiosis.–Explain the consequences of mistakes.

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Cell Size

•Why not just one large cell?•Difficult to get nutrients in and waste out

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Phases of The Cell Cycle

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G1,S, and G2 are known together as Interphase.

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Somatic cell cycle • G1 phase- Gap phase, cell

undergoes growth.

• S phase- DNA synthesis

• G2 phase- Gap phase. Preparation for Mitosis. Organelles are produced.

• M phase- Cell division (Mitosis and cytokinesis)

Interphase

Regular Cells

Sex cells are

called gamete

s

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G1 Phase

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•Cell Grows

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S Phase• Chromosomes

Condense• Chromosomes

are inherited genetic information

• Chromosomes are made up of DNA

• Can only be seen when cells are dividing

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S Phase• Chromosomes Chromosomes

replicate-or copy is replicate-or copy is mademade

• The two copies areThe two copies are• --attached together at a attached together at a

point called a point called a centromerecentromere..• -are called sister -are called sister

chromatidchromatid..

When a cell divides, its two daughter cells must receive the required number of DNA molecules.

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GG2 2 PhasePhase

Organelles must be Organelles must be replicated (copied)replicated (copied)

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M PhaseM PhaseTwo parts:Two parts:

1.1.Nuclear divisionNuclear division– MitosisMitosis

2.2.Cytoplasmic DivisionCytoplasmic Division– CytokinesisCytokinesis

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MitosisMitosis• Nuclear Division.• Nucleus divides into two new nuclei

Mitosis keeps the number of chromosomes constant from one cell generation to the next.

• In eukaryotes, it is the main process by which growth and tissue repair is accomplished.

• Mitosis is also the main process by which single-celled and many multi-celled eukaryotes reproduce asexually.

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4 Steps of Mitosis (PMAT)•  Prophase: Chromosomes condense and attach to

the spindle fibers at their centromere.

• Nuclear

Membrane

breaks down.

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Steps of Mitosis (PMAT)•   Prophase: Prophase: Centrioles move to opposite sides of Centrioles move to opposite sides of

the cell and organize the spindle fibersthe cell and organize the spindle fibers

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Metaphase:Metaphase: Chromosomes attach to

spindle fibersand line up in the middle

of the cell

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Anaphase: Chromosomes separate-Move to opposite sides of the cell

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Telophase• Nuclear Envelope reforms

There are now TWO nuclei in one cell!

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…And they contain the

SAME genetic information

*SAME NUMBER OF

CHROMOSOMES

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CytokinesisCytokinesis• Cytoplasmic divisionCytoplasmic division• Each cell gets half of the Each cell gets half of the

organelles.organelles.• After mitosis: cell pinches After mitosis: cell pinches

in half to form two new in half to form two new cells.cells.

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CytokinesiCytokinesiss

•Animal cells Animal cells pinch. pinch.

•Cytokinesis in Cytokinesis in plant cells is plant cells is different from different from that in animal that in animal cells.cells.

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In plant cells a cell plate forms from the inside out.•

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•TwoTwo new cells.•The new cells- called daughter cells-called daughter cells- have the same number of same number of chromosomeschromosomes as the mother cell.

Results of Mitosis and Results of Mitosis and CytokinesisCytokinesis

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Results of Mitosis and Results of Mitosis and CytokinesisCytokinesis

•This occurs in all somatic cells in your body.

•You have 46 chromosomes in all of your somatic cells-23 pair!

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Mitosis in Onion25

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Cells during Mitosis

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http://www.youtube.com/watch?v=VlN7K1-9QB0&feature=related

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includes

is divided into

is divided into

Concept Map

Cell Cycle

M phase (Mitosis)

Interphase

G1 phase

S phase

ProphaseG2 phase

Metaphase TelophaseAnaphase

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Meiosis:Reproduction of Sex

Cells•Sex cells- Sperm and egg•Process is called Meiosis•Similar to Mitosis

Meiosis Introduction Clip

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MeiosisMeiosis•Cell divides Cell divides

twicetwice•First division is First division is

like mitosis like mitosis and then the and then the cell divides cell divides again to create again to create 4 haploid cells.4 haploid cells.

Not genetically identical!Contains ½ (HAPLOID) of the genetic information.

DIPLOID= 2 copies)31

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Not genetically identical!Contains ½ of the genetic

information.

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MEIOSIS=CHROMOSOME REDUCTION DIVISION

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Not genetically identical!Contains ½ of the genetic

information.

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MeiosisMeiosis• Meiosis is also know as Meiosis is also know as

chromosome reduction division.chromosome reduction division.• In Humans, starts with 46 and In Humans, starts with 46 and

ends up with 23.ends up with 23.• Why?Why?• Fertilization creates the diploid Fertilization creates the diploid

condition againcondition againDiploiDiploidd

HaploidHaploid

34 Meiosis Square Dance

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• Sperm formationSperm formation- 4 haploid sperm cells are formed.

• Egg formationEgg formation-most of the cytoplasm is used in one cell and the other three disintegrate. One haploid egg cell is formed.

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Meiosis

Video ClipVideo Clip

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Crossing Over• Sometime

during meiosis the chromosomes can exchange information

• This is called Crossing Over

• Major source of genetic diversity in the species

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Prokaryotic CellsProkaryotic Cells

• Binary fission

• Occurs in Prokaryotic Cells

• DNA is copied and then the cell splits in half.

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Regulation of the Cell Cycle

• How do cells know when to divide?

• When to stop dividing?

• Cyclins-proteins that regulate the cell cycle.

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Cancer

•Unregulated cell growth.

•Can form masses of cells called tumors.

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